Underfell AU Two-shot: Sans Battle
by nyacat39
Summary: After many falls against the corrupted Sans, Frisk finally makes it to the ACT feature.
1. Chapter 1

Hey everyone, this is my first official thing for the Underfell AU for Undertale... and more then likely my last as this was literally just a spur of the moment idea that I spent like an hour typing on my Tumblr before deciding "Hey it's gotten pretty popular here so why not post it on my Fanfiction see how that goes!" plus it's like almost 1 AM while I'm typing this note out.

Anyways hope y'all like it!

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Frisk stood there in the Last Corridor gasping and trying to hold back as many tears of pain as they could. Sans stood not to far away from them, preparing another attack from the Gaster Blasters with a sadistic grin on his skeletal face.

"to bad you didn't gain any LOVE kid other wise you wouldn't have DIED this much so easily," Sans laughed, glowing red eyes trained on the child.

"Frisk..." Flowey's voice pipped up quietly, concerned for their gravely injured friend. "I... I know I've been saying this a lot but... but I really do think you need to kill him this time. Sparing the others and showing them Mercy may have helped before but-"

Frisk shook their head immediately. They were not going to stop, not until they got their last friend back... and fix this corrupted save file. Taking one step forward with the goal in mind caused Sans to fire the Blaster at the child who barely dodged and ended up biting their lower lip to prevent screaming out in pain. Blood soon started to trickle down not just the new wound but also from the bitten lip.

"just give up and stay dead already kid," Sans growled, slowly getting more and more annoyed as the child kept coming back. Frisk however stayed determined and kept moving forward towards Sans. Each step they took ended up with Sans attacking them more with his magic, and more damage to Frisk.

"Frisk please just fight him!" Flowey cried out, the need to cry strong as the flower continued to watch their friend get hurt.

Frisk however, continued on their walk, eyes forward and breath heavy as they got closer and closer to Sans despite all the attacks. Finally, despite being left with only one HP, Frisk was now in front of Sans who's eye sockets were wide with surprise, before narrowing quickly as another magic attack began to be charged. Now was the time... to ACT.

Frisk reached out and wrapped their small arms around Sans as much as they could, making the skeleton flinch and try to push the child off.

"get off me you brat!"

Frisk refused and finally hit the ACT menu once again. Taking a deep breath they began to speak, through both memories of the time before the SAVE file was corrupted and through their very heart.

"stop it."

Frisk continued, slowly loosing control over their own tears as they began to fall down the child's cheeks and into the black jacket that Sans wore. They continued to speak though. Making promises and apologizing.

"i said STOP it!"

Sans began summoning his bone magic and stabbing into the child... but they stood there despite it all and cried more while apologizing more.

"why won't you die already?!" despite the continued attack from the skeleton... it was obvious even he was beginning to wear down.

Frisk continued, with one final promise... one that they knew Sans would want more than anything.

"I promise to never reset again!"

Everything stopped. Frisk continued to hold on to Sans, tears still rolling down and mixing with their own blood. Sans stood in silence, eyes trained right on the child whose breathing continued to get heavier, through both the pain they were in as well as from all their tears.

The last promise made had brought a small flash of... memories to the skeleton of a time before the corruption. The joy from it was real... the feel of everything in it was real... the human child holding his hand and laughing in the memory was real... Toriel... Toriel and the human in the memory... smiling and having fun were real.

Unknowingly as the two stood there, some tears began to fall from the skeleton's eye sockets around the same time the light in Frisk's eyes began to fade.

"... kid?"

No response came from the human. Before Sans could try speaking again the ever familiar red heart appeared before his eyes... before shattering once again.


	2. Chapter 2

I hope you're all happy... I made it a two shot because SOME PEOPLE (glares at one friend in particular) couldn't handle the fact it was a one shot that was left off on such a painful note.

* * *

As the soul shattered a ring of green Friendliness Pellets surrounded the shards and pushed them all back together, fixing the soul and healing Frisk back to one HP. As soon as it was fixed Frisk's eyes closed and light breathing could be heard from the child as they began to leave heavily against Sans. The skeleton's eye sockets still had small streams of red tinted tears rolling out of them.

"Let them go..." Flowey muttered, tears of his own being shed from his own eyes as he mustered up enough strength to send a glare as Sans. Sans however stood motionless, hands still on the child's shoulders and shock still clear on his features.

"LET THEM GO ALREADY!" Flowey shouted, snapping Sans out of his shocked stupor enough to have the red eyes focus on the damaged yellow flower.

"Haven't you done them enough damage to them already?!"

"... hey kid..." Sans started, ignoring the flower, who continued to shout at Sans. Flowey desperately wanted to get Frisk away from Sans, who they still saw as a danger and really wanted to attack the skeleton... but with Frisk in the way they didn't want to hurt their only friend.

"when you wake up i'll spare ya, got it. don't come looking for me after or try talking to me. i'll just tell ya to screw off and attack you again... but when you do wake up... keep going alright. go ahead and fix everything. remember your promise to never reset alright?" Sans finished, glancing down at the out cold human, whose lips seemed to curl into a small smile while they slept.

The skeleton carefully laid the child down onto the ground before stuffing his hands into the pockets on his jacket and casually started to walk off.

"oh by the way weed," Sans spoke up as he started passing by Flowey, who sat in his little make shift pot with a dumbfounded expression.

"enjoy your time with the kid while it lasts."

With that said Sans vanished, leaving behind a confused flower and a sleeping child. Flowey sat there for a short while before using a little more green magic on Frisk, healing them back up to 20 HP, while cautiously questioning what Sans meant... as well as if they actually saw a flash of blue in those red eyes.


End file.
